«

"Steve B" <> writes:

> "Peter Jason" <> wrote in message
> news:...
>> Like laser pinpointing on rifles and pistols.
>>
>> I need it for shooting from the hip at weddings
>> and the like when the exposure is set for
>> pinpoint.
>>
>> Peter
>
> Bad, bad, bad.
> Endangers eyesight.

Class 1 lasers are safe "under all conditions of normal use" including
using optics to concentrate the power. Some laser pointers are Class 2
or 2m, and are safe if they're visible light (not infrared) because they
won't damage your eye faster than you can blink (and aren't any threat
to anything less sensitive than your retina).

Lots of fear about lasers around, but what you can easily get are hard
to hurt yourself with.
--
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In article <>, Alfred
Molon <> wrote:

> > > Lots of DSLRs or interchangeable lens cameras with tiltable LCD screens
> > > around. Why wouldn't a pro use them?
> >
> > You won't find that sort of feature above the consumer-level produts; in
> > the Nikon line (the one I know) it's not on the D700, D800, or D4 (or
> > older models at that level).
>
> Actually lots of DLSRs and interchangeable lens cameras, good enough for
> a "pro", have a tiltable LCD screen.

those cameras may be good enough in some situations, but pros don't
generally use those cameras outside of a backup, and if they do, they
don't use the tiltable lcd anyway.

In message
<7de8004d-9688-4001-bf5a->,
RichA <> writes
>
>I'm wondering though, if a weak IR laser would produce a visible laser
>spot on a subject via viewing through an EVF or LCD? If so, it might
>be possible to do what the op wanted without risking any injury or
>annoyance with the people he's shooting at?

Just because you can't see an infrared laser doesn't make it safe! Quite
the opposite, an IR laser beam doesn't provoke a blink reaction or
contraction of the eye pupil, as a visible laser would. Consequently
the laser gets focussed on the retina without any natural restriction,
causing much greater retinal damage. You don't get into the so called
"eye safe" region until you are up around 1.5um, well beyond the
response cut-off of silicon so it wouldn't show up on the EVF. Even
then, the "eye-safety" is only achieved by absorption of the beam
through the vitreous humour (the internal fluid in the eye) which isn't
total, so there are still dangerous levels especially at close
distances. For example, infrared laser rangefinders have minimum eye
safe ranges.
--
Kennedy

In article <>, Eric Stevens
<> wrote:

> >> > > Lots of DSLRs or interchangeable lens cameras with tiltable LCD
> >> > > screens around. Why wouldn't a pro use them?
> >> >
> >> > You won't find that sort of feature above the consumer-level produts; in
> >> > the Nikon line (the one I know) it's not on the D700, D800, or D4 (or
> >> > older models at that level).
> >>
> >> Actually lots of DLSRs and interchangeable lens cameras, good enough for
> >> a "pro", have a tiltable LCD screen.
> >
> >those cameras may be good enough in some situations, but pros don't
> >generally use those cameras outside of a backup, and if they do, they
> >don't use the tiltable lcd anyway.
>
> Not true.
>
> I've several times seen 'a pro' (several in fact) using a Canon DSLR
> with a tiltable screen to enable them to see what they are doing when
> setting their cameras up for peculiar shots from a tripod. I've
> envied the flexibility that such a screen gave to their work.

several out of millions of pros does not mean it's common. it's the
exception, not the rule.

In article <gIe2bAE$GH+QFw+>, Kennedy McEwen
<> wrote:

> >I'm wondering though, if a weak IR laser would produce a visible laser
> >spot on a subject via viewing through an EVF or LCD? If so, it might
> >be possible to do what the op wanted without risking any injury or
> >annoyance with the people he's shooting at?
>
> Just because you can't see an infrared laser doesn't make it safe! Quite
> the opposite, an IR laser beam doesn't provoke a blink reaction or
> contraction of the eye pupil, as a visible laser would. Consequently
> the laser gets focussed on the retina without any natural restriction,
> causing much greater retinal damage. You don't get into the so called
> "eye safe" region until you are up around 1.5um, well beyond the
> response cut-off of silicon so it wouldn't show up on the EVF. Even
> then, the "eye-safety" is only achieved by absorption of the beam
> through the vitreous humour (the internal fluid in the eye) which isn't
> total, so there are still dangerous levels especially at close
> distances. For example, infrared laser rangefinders have minimum eye
> safe ranges.

yet every day, police point infrared lasers at oncoming cars. although
they may aim at the license plate, plenty of the laser still hits the
eyes of the occupants of the vehicle. it's also 904 nm, well below your
1.5 um limit.

In message <170120131846285546%>, nospam
<> writes
>In article <gIe2bAE$GH+QFw+>, Kennedy McEwen
><> wrote:
>
>> >I'm wondering though, if a weak IR laser would produce a visible laser
>> >spot on a subject via viewing through an EVF or LCD? If so, it might
>> >be possible to do what the op wanted without risking any injury or
>> >annoyance with the people he's shooting at?
>>
>> Just because you can't see an infrared laser doesn't make it safe! Quite
>> the opposite, an IR laser beam doesn't provoke a blink reaction or
>> contraction of the eye pupil, as a visible laser would. Consequently
>> the laser gets focussed on the retina without any natural restriction,
>> causing much greater retinal damage. You don't get into the so called
>> "eye safe" region until you are up around 1.5um, well beyond the
>> response cut-off of silicon so it wouldn't show up on the EVF. Even
>> then, the "eye-safety" is only achieved by absorption of the beam
>> through the vitreous humour (the internal fluid in the eye) which isn't
>> total, so there are still dangerous levels especially at close
>> distances. For example, infrared laser rangefinders have minimum eye
>> safe ranges.
>
>yet every day, police point infrared lasers at oncoming cars.

Not at close enough range to risk damage though.

>although
>they may aim at the license plate, plenty of the laser still hits the
>eyes of the occupants of the vehicle.

Sure, and it can illuminate the occupants because at the range at which
it is used the beam covers a large enough area to extend to them even
when centred on the number plate. People seem to think that a laser
beam can only ever be the pencil thin beam they see at light shows or
produced by laser pointers. They can be very thick beams, created by
beam expanding optics, reducing the danger level significantly. The
exit pupil of a typical speed gun laser is around 40-50mm, not the 1-2mm
of a laser pointer. They can also be very divergent, reducing the
intensity, and danger, very quickly with range.

Even so, laser speed guns also have minimum nominal optical hazard
distances (NOHD) below which they are dangerous to use.
--
Kennedy

In article <2013011717181923810-savageduck1@REMOVESPAMmecom>,
Savageduck <savageduck1@{REMOVESPAM}me.com> wrote:

> >> although
> >> they may aim at the license plate, plenty of the laser still hits the
> >> eyes of the occupants of the vehicle.
> >
> > Sure, and it can illuminate the occupants because at the range at which
> > it is used the beam covers a large enough area to extend to them even
> > when centred on the number plate. People seem to think that a laser
> > beam can only ever be the pencil thin beam they see at light shows or
> > produced by laser pointers. They can be very thick beams, created by
> > beam expanding optics, reducing the danger level significantly. The
> > exit pupil of a typical speed gun laser is around 40-50mm, not the
> > 1-2mm of a laser pointer. They can also be very divergent, reducing
> > the intensity, and danger, very quickly with range.
> >
> > Even so, laser speed guns also have minimum nominal optical hazard
> > distances (NOHD) below which they are dangerous to use.
>
> a "Ladar/Lidar" spot at typical ranges is huge and paints more than
> just the number plate. Typically the entire front of the car is painted
> including the area of the windshield. This allows the Laser detector in
> the car to inform you that you are about to receive a ticket. At 2000ft
> the "spot" has a diameter of about 6ft. The Officer is not aiming by
> placing the "spot" on the numberplate, he/she is using an optical sight
> integrated into the unit. Speed detection Lasers are usually contained
> Class I lasers.

the officer uses the optical sight in the lidar gun to aim at the car's
license plate or headlights because those are the most reflective. the
beam width at a typical measuring distance will cover more than just
the license plate, including the rest of the vehicle and quite possibly
other vehicles.

On Thu, 17 Jan 2013 21:48:47 +0000, Kennedy McEwen <>
wrote:
: In message
: <7de8004d-9688-4001-bf5a->,
: RichA <> writes
: >
: >I'm wondering though, if a weak IR laser would produce a visible laser
: >spot on a subject via viewing through an EVF or LCD? If so, it might
: >be possible to do what the op wanted without risking any injury or
: >annoyance with the people he's shooting at?
:
: Just because you can't see an infrared laser doesn't make it safe! Quite
: the opposite, an IR laser beam doesn't provoke a blink reaction or
: contraction of the eye pupil, as a visible laser would. Consequently
: the laser gets focussed on the retina without any natural restriction,
: causing much greater retinal damage. You don't get into the so called
: "eye safe" region until you are up around 1.5um, well beyond the
: response cut-off of silicon so it wouldn't show up on the EVF. Even
: then, the "eye-safety" is only achieved by absorption of the beam
: through the vitreous humour (the internal fluid in the eye) which isn't
: total, so there are still dangerous levels especially at close
: distances. For example, infrared laser rangefinders have minimum eye
: safe ranges.

And any energy absorbed in the vitreous humor expresses itself as heat, and
artifically heating up the eyeball isn't usually considered desirable.

Bob

On Thu, 17 Jan 2013 18:23:49 -0800, Savageduck
<savageduck1@{REMOVESPAM}me.com> wrote:
: On 2013-01-17 17:59:31 -0800, nospam <> said:
:
: > In article <2013011717181923810-savageduck1@REMOVESPAMmecom>,
: > Savageduck <savageduck1@{REMOVESPAM}me.com> wrote:
: >
: >>>> although
: >>>> they may aim at the license plate, plenty of the laser still hits the
: >>>> eyes of the occupants of the vehicle.
: >>>
: >>> Sure, and it can illuminate the occupants because at the range at which
: >>> it is used the beam covers a large enough area to extend to them even
: >>> when centred on the number plate. People seem to think that a laser
: >>> beam can only ever be the pencil thin beam they see at light shows or
: >>> produced by laser pointers. They can be very thick beams, created by
: >>> beam expanding optics, reducing the danger level significantly. The
: >>> exit pupil of a typical speed gun laser is around 40-50mm, not the
: >>> 1-2mm of a laser pointer. They can also be very divergent, reducing
: >>> the intensity, and danger, very quickly with range.
: >>>
: >>> Even so, laser speed guns also have minimum nominal optical hazard
: >>> distances (NOHD) below which they are dangerous to use.
: >>
: >> a "Ladar/Lidar" spot at typical ranges is huge and paints more than
: >> just the number plate. Typically the entire front of the car is painted
: >> including the area of the windshield. This allows the Laser detector in
: >> the car to inform you that you are about to receive a ticket. At 2000ft
: >> the "spot" has a diameter of about 6ft. The Officer is not aiming by
: >> placing the "spot" on the numberplate, he/she is using an optical sight
: >> integrated into the unit. Speed detection Lasers are usually contained
: >> Class I lasers.
: >
: > the officer uses the optical sight in the lidar gun to aim at the car's
: > license plate or headlights because those are the most reflective. the
: > beam width at a typical measuring distance will cover more than just
: > the license plate, including the rest of the vehicle and quite possibly
: > other vehicles.
:
: Thank you for your endorsement of all I have written on the subject, by
: paraphrasing it and adding the typical aim points to the explanation.
:
: My main point is that with the diffused "LiDAR" beam there is not going
: to be a spot visible anywhere on the target vehicle as there might be
: with a pointer or firearms laser sight and the officer has no choice
: but to use the optical sight to aim at numberplate, headlights or grill.
:
: Also the big disadvantage over vehicle installed Radar speed detection
: is, the Lidar unit has to be stationary. So watch those overpasses and
: hidden pullouts. The CHP will only use Lidar from stationary positions
: whereas CHP cruisers use cycling front and rear facing Radar and are
: able to clock following and head on closing vehicles. So there are
: times when slowing down after you understand that car you coming up to
: with the intention of passing is a CHP cruiser and your ticket is as
: good as written.

Well, if you slow down, it tells the cop that at least you were paying
attention. If he's having a good day, that might possibly tip the balance
between a fine and a warning.

Bob

In article <2013011718234977633-savageduck1@REMOVESPAMmecom>,
Savageduck <savageduck1@{REMOVESPAM}me.com> wrote:

> Also the big disadvantage over vehicle installed Radar speed detection
> is, the Lidar unit has to be stationary. So watch those overpasses and
> hidden pullouts. The CHP will only use Lidar from stationary positions
> whereas CHP cruisers use cycling front and rear facing Radar and are
> able to clock following and head on closing vehicles. So there are
> times when slowing down after you understand that car you coming up to
> with the intention of passing is a CHP cruiser and your ticket is as
> good as written.

only if you're oblivious.

> What is tough for Radar to do is isolate an individual vehicle to
> clock. That takes experience and/or LiDAR.

supposedly, they estimate the speed visually and confirm it with radar
(or lidar), so they already know which car it is.

on the other hand, a lot of times they just wait for the overspeed
alarm to go off.